Device for amplifying variations in electrical currents.



P. M. RAINEY. DEVICE FOR AMPLIFYING VARIATIONS IN ELECTRICAL GURRBNTS.

Patented Apr. 7, 19M

APPLICATION FILED 001. 14, 1913.

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v nnnnnnnn UNITED STATES PATENT OFFICE.

PAUL M. RAINEY, OF WEST HOBOKEN, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF NEW YORK, N. Y., A CORPORATION" OF ILLINOIS.

DEVICE FOR AMPLIFYING VARIATIONS IN ELECTRICAL CURRENTS.

Specification of Letters Patent.

Patented Apr. 7, 1914.

Application inea'octobei '14, 1913. Serial No. 795,124.

To all 2072 0222 it may concern:

Be it known that I, PAUL M. RAINEY, a citizen of the United States, residingat West Hoboken, in the county of Hudson and State of New Jersey, have invented a certain new and useful Improvement in Devices for Amplifying Variations in Electrical Currents, of which the following is a full, clear, concise, and exact description,

This invention relates to a device for amplifying variations in electrical currents, and more particularly to a device for amplifying current variations such as are ordinarily encountered in telephonic transmission, such devices being commonly termed telephone relays or repeaters.

It is an object of this invention to utilize in a telephone repeater that property of certain magnetic materials, by virtue of which a change in length of a given piece of material is brought about by means of variations in the intensity of the magnetizing force to which such piece of material is subj ected. This property of magnetic materials is generally termed magneto-striction, and the quantity of the effect produced thereby varies for different materials. It has been determined experimentally that when certain materials, notably Norway iron and low carbon steels, are subjected to gradually increasing magnetizing forces, a piece of such material first increases in length with an increase magnetizing force until a given magnetizing force is reached, and thereafter decreases in length with an increase in magnetizing force. Owing to this peculiar characteristic of certain materials, it is possible, by adjusting the intensity of the magnetizing forces acting upon two or more mechanically connected pieces of such materials, to obtain the combined effect of the expansion of one piece and the contraction of the other due to variations of the total "magnetizing forces.

Itis an object of the present invention to utilize such combined effect and to produce" by such effect, variations in the resistance of an ordinary microphone. As the microphone may be connected in an independent circuit with a source of energy, and the magnetizing forces, which affect the variations in length of the pieces of magnetic-material, may be produced by means of the incoming currents, the variations in the incoming currents will correspondingly vary the resistance of the microphone and produce amplified variations in the microphone circuit.

For a more complete understanding of the invention, reference may be had to the accompanying drawing, wherein- Figure 1 is a longitudinal sectional View of one form of repeater embodying the invention; Fig. 2 is a similar view of a modified form; and Fig. 3 is a curve indicating the magneto-striction characteristic of Norway iron. 1

In Fig. 3 of the drawing, there is shown the magneto-striction curve for Norway iron, plotted with fractional change in length as ordinates, and intensity of magnetizing force as abscissae. From an inspection of this curve, it will be seen that as the intensity of magnetizing force increases from zero to approximately 50 units, the fractional change of length in the piece of material under test also increases, While any increase in the intensity of the magnetizing force beyond 50 units is accompanied by a relative decrease in the fractional change in length.

The intensity of magnetizing force acting on any element of a magnetic circuit depends on the ampere turns acting and the reluctance of the element relative to that of the whole circuit. It is then possible to adjust the intensity of the magnetizing force at any given point in the magnetic circuit by adjusting the number of ampere turns of the magnetizing coil and the cross-section of the piece of magnetic material acted upon. Therefore, by employing two pieces of magnetic material, either in the same or a separate magnetic circuit, it is possible to produce a normal intensity of magnetizing force in one piece corresponding to that represented by a point a on the curve, and

, dependent circuits.

terial are connected at one end by a piece of non-magnetic metal 3. The other end of the rod- 2 is connected by means of a set screw 4 in a socket of a bracket 5. A bracket 6, se-

cured to the crosspiece 3,'is made of spring granule-containing chamber 8 is provided with a shank 10 which passes through an aperture in a bracket 11 and is held therein by a set screw 12. Mounted within the chamber 8 is a stationary electrode 13, and the electrodes 7 and 13 with the carbon granules therebetween form an ordinary microphone.

The rods 1 and 2 are each provided with two windings 29, 14 and 15, 16 respectively. The windings 14; and 16 are connected in series and form part of the incoming circuit. The windings 29 and 15 may be connected in series or may form parts of two entirely in- The purpose of the windings 29 and 15 is to regulate the normal or steady intensity of the magnetizing force acting on the rods. The current is so adjusted that the intensity of the magnetizing force acting on the rod 2 approximates the intensity indicated at the point a on the curve of Fig. 3, and the intensity of magnetizing force acting on the rod 1 corresponds to the intensity indicated at c on-the curve. Variations in the current of the incoming circuit will, owing .to the fact that the windings 14 and 16 are in series, cause corresponding variations in the magnetizing forces acting on the rods 1 and 2. As these changes in magnetizing force occur in the case of rod 1 adjacent the point 0 on the curve, and in the case of rod 2 adjacent the point a on the curve,-the rod 1 will decrease in length uponan increase in magnetizing force, and the rod 2 will relatively increase in length upon an increase in magnetizing force so that the electrode 7 of the microphone will be dlsplaced an amount equal to the sum of the increase in rod 2 and the decrease in rod 1, and vice versa upon a decrease in magnetizing force. This will cause the variation in the resistance bet-ween the electrodes 7 and 10 and in the local cir cuit connecting said electrodes.

In the form of the repeater shown in Fig.

' 2, a rod and a cylinder, both of magnetic material, replace the two rods of the repeater, Fig. 1. The rod and cylinder, however, are part of the same magnetic circuit, and the magnetizin windings are placed upon the rod. In t is form of repeater a cylinder 17 of magnetic material is threaded into an aperture in a bracket 18. The other end of the cylinder 17 is closed by a cap 19 of magnetic material, which cap, in conjunction with a resilient diaphragm 20 of magnetic material, serves'to support a rod of magnetic material 21 centrally in the cylinder. The cylinder is supported at the end opposite from the diaphragm 20 by means of a yielding bracket 22, which permits longitudinal movement of the cylinder. One end of the rod 21 is fixedly secured to the-cap 19, and the other end of said rod is connected to anelcctrode 23 of a microphone 24. The other electrode of the microphone is indicated at 25. The microphone 24 is secured to a bracket 26 by means of a set screw'27. The rod 21 is provided with two windings 30 and 28, the winding 30 being connected in an independent circuit, and the winding 28 being connected to the incoming circuit. The proportional division of the total normal or steady magnetizing force acting on the magnetic circuit is obtained by proportioning the relative sectional areas of the rod 21 and the tube 17. The current flowing in the circuit of the winding 30 is adjusted so that the intensity of the magnetizing force acting on the rod corresponds approximately to the intensity indicated at the point a on the curve, and the intensity of the magnetizing force acting in the cylinder 17 approximates the intensity indicated at point 0 on the curve. WVhen current variations are impressed on the winding 28 with an increase in magnetizing force, there is a tendency for the rod 21 to increase in length, and for the cylinder 17 to decrease in length, and the sum of these two effects is transmitted to the movable electrode 23 of the microphone 24. Likewise for a decrease in magnetizing force, there is a tendency for the rod 21 to decrease in length, and for the cylinder 17 to increase in length, and the sum of'these two effects is transmitted to the movable electrode 23 of the microphone 2 1. As in the case of the relay of Fig. 1, the microphone is connected in a local circuit, and the variations in the resistance of the microphone, due to the variation in length of the rod 21 and cylinder 17, correspond to'the variations in the incoming circuit.

Owin change 1n length of a given piece of magnetic material due to a change in magnetizing force is comparatively small, it has been found diflicult to utilize such change in length in a telephone repeater, but by using two or more pieces of material and acting on such pieces at different intensities of magnetizing force, it is possible to magnify this effect to such an extent as to make a'prac-.

tical repeater. It is obvious, that if more to the. fact that the amount of than two rods of different cross-sections are tional area could be used by varying the number of ampere turns acting upon said rods.

I claim: Y

1. In a telephone repeater, a plurality of pieces of magnetic material, means for normally subjecting certain of said pieces to steady magnetizing forces of low intensity,

. and others of said pieces to steady magnetizable resistance element.

2. In a telephone repeater, a magnetizing coil in'the incoming circuit and a variable resistance device in the local or outgoing circuit, a plurality of cores for said coil, means for normally subjecting some of said cores to steady magnetizing forces of low intensities and other of said cores to steady magnetizing forces of relatively high intensities, and means for connecting said cores to each other, to a support and to a movable member of said variable resistance device.

3. A telephone repeater comprising a plurality of pieces of magnetic material, means for normally subjecting some of said pieces to steady magneti'zin forces of low mtenslty and othersof sai pieces to steady magnetizing forces of relatively high intensity,

other of said pieces,

means for impressing a variable magnetizing force on said pieces and causing by such variable force an lncrease in length of some of said pieces and a decrease in length in and means for connect ing said pieces to each other, to a support and to a variable resistance element, whereby a movable member of such resistance element is moved a distance equal to the sum of the variations in length of said pieces.

4. In .a telephone repeater apparatus, a microphone element embracing a movable member, magnetic members operatively ,connected with the movable member of said microphonic element, means controlling directionally opposite length changes in said magnetic members, and means for varying said length changes in saidmembers, whereby said movable element is moved a distance equal to the combined change in length of said magnetic members.

5. In a telephone repeater apparatus, a variable resistance device, a plurality of magnetic members operatively connected with said variable resistance device, means for causing some of said magnetic members to expand and others to contract, and means for varying the expansion and contraction of said magnetic members to vary the resistance of said variable resistance device.

In witness whereof, 'I hereunto subscribe my name this 10th day of October A. D.,

PAUL M. RAINEY.

Witnesses:

ROY C. HAPcooD, ALICE HAZLEY. 

